1. Field of the Invention
The present invention relates to an airbag gas generator to protect a passenger against impacts and more particularly to an airbag gas generator characterized by its unique operating performances.
2. Description of Related Art
Motor vehicles such as automobiles have an airbag system, which protects a passenger from getting injured or killed. When a vehicle crashes at a high speed, the air bag system rapidly inflates an airbag with a gas to prevent a passenger from hitting against hard or dangerous portions, such as a steering wheel and windshield inside the vehicle, due to inertia.
Such an airbag system should preferably be able to safely hold the passenger, whatever his or her build (which may vary depending on the passenger's sitting height or whether the passenger is an adult or child) or the riding posture (some drivers may cling to a wheel) . To meet this requirement, airbag systems which operate to apply as small an impact as possible to the passenger at the initial stage of activation have conventionally been proposed.
JP-A 8-207696 proposes an airbag system that uses two kinds of gas generating capsules to produce a gas in two stages, with the first stage inflating the bag relatively slowly and the second stage causing a rapid gas generation. This system, however, has a drawback that the structure inside the gas generator is complicated, which in turn increases the size of a container and therefore increases the manufacturing cost.
U.S. Pat. Nos. 4,998,751 and 4,950,458 also propose airbag systems that have two combustion chambers for burning a gas generating agent in two stages to restrict the operating function of the gas generator. These systems, however, are complex in structure and not satisfactory.